1. Field of the Invention
The present invention relates to a liquid discharge device that discharges liquid from a main tank to a sub tank that is arranged on a carriage.
2. Description of the Related Art
Ink jet printers having a so-called stationary supply mechanism are known. With the stationary supply mechanism, a sub tank that is capable of storing a small amount of ink is arranged on a carriage. A print head used to print on a printing medium is also arranged on the carriage. Ink is supplied to the print head from the sub tank. A main tank that is capable of storing a large amount of ink is attached to a position separate from the carriage. The carriage is capable of moving. When the carriage is located at an ink supply position, the sub tank and the main tank are temporarily connected, for instance, with a supply nozzle, and ink is replenished from the main tank to the sub tank.
In the case of ink jet printers using the stationary supply mechanism, impurities such as dust or dried ink may adhere to the distal end of the supply nozzle. In this case, the impurities may be transferred into the sub tank in the course of connecting the supply nozzle to the sub tank. Moreover, there is a substantial possibility that the impurities adhered to the inside of the distal end of the supply nozzle will be transferred into the sub tank.
Once such impurities are transferred into the sub tank, it is almost impossible to remove them from the sub tank. Such impurities give rise to undesirable conditions such as clogging of a filter inside the sub tank. Also, with impurities inside the supply nozzle, efficiency of ink replenishment is hindered. For example, in the case of detecting the amount of ink inside the sub tank with a sensor, if ink cannot be replenished efficiently, a longer time period is needed for the replenishing process. Furthermore, in the case of replenishing ink using a timer, necessary amount of ink may not be supplied to the sub tank within the allowed time period.
The Japanese Patent Application Publication No. 2001-162830 discloses an ink jet printer having a cleaning device for removing impurities adhering to a supply nozzle of a main tank. The supply nozzle is supported by a rotatable supporting stand. The supply nozzle can be rotated to face a sub tank and be inserted into the sub tank to replenish ink to the sub tank. The supply nozzle and its supporting stand can be rotated to face the cleaning device, and moved to insert the supply nozzle therein. Then, the impurities adhering to the supply nozzle is brushed off with a brush of the cleaning device. In this technique, a process of cleaning the supply nozzle is performed during a stand-by status.